Abrasive disc machine for resurfacing slate, wood, metal, plastics, or the like



Apnl 1, 1958 R. P. MILLER 2,828,587

ABRASIVE DISC MACHINE FOR RESURFACING SLATE, WOOD, METAL, PLASTICS, ORTHE LIKE Filed Sept. 17; 1956 r 2 Sheets-Sheet 1 INVENTORQ ROBERT P.MILLER ATTOR N EY Aprll 1958 R. P. MILLER 2,828,587

ABRASIVE DIsc MACHINE FOR RESURFACING SLATE, woon, METAL, PLASTICS, ORTHE LIKE Filed Sept. 17, 1956 2 Sheets-Sheet 2 INVENTOR.

ROBERT P. MILLER ATTORNEY ABRASIVE DESC MAQHHNE FUR REURFAENGISJIIJIAI'EIE, W093), METAL, PLASTICS, GK THE Robert P. Miller, NewSevvickley Township, Beaver County, Pa.

Application September 17, 195-6, Serial No. 610,128

' Claims. (Cl. 51-450) In the past there have been machines for theresurfacing of slates such as those commonly used as blackboards forschool and other purposes. Such blackboards after continual use becomebadly pitted and irregular, often making them unfit for any furthersatisfactory use. Often the prior machines have been satisfactory, butmore often their use has ground the slate in such fashion that the boardmust be destroyed and replaced. Such unsatisfactory grinding is oftenthe result of the application of irregular pressure to the grindingtool, resulting in the development of an undulating or wavy surface thatis not satisfactory for use.

An object of my invention is to provide a grinding head or disc whichwill be maintained constantly in one fixed position.

A further object is to provide a grinding disc to which a proper andregular grinding pressure is constantly applied while the disc is inoperation.

An additional object is to provide a grinding disc which is drawn intogrinding contact by vacuum suction which at the same time removes anyelements which have been ground away from the slate being resurfaced.

An even further object is to provide a grinding disc which may beadjusted to varying heights on the slate to t be ground.

Further objects will become apparent from an understanding of thedrawings forming a part of the application, and the detailed descriptionof the machine.

In the drawings:

Figure 1 is a view in back elevation;

Figure 2 is a view in side elevation showing the grinding disc inoperating position, but not showing its supporting truck or dolly;

Figure 3 is an enlarged view in vertical cross section through thegrinding head, and partly broken away; and

Figure 4 is a view in front elevation showing the grinding head and itssupporting arm.

My resurfacing machine is preferably mounted on a suitable wheeledplatform or dolly 1% which carries a conventional electric motor andgear box within the casing 12. A shaft extends from the reduction gearwithin the gear box and carries a sprocket wheel 14 around which istrained a link drive chain 16 which is likewise trained around asprocket (not shown) keyed to the axle which carries the drive Wheel 18of the wheeled platform or dolly. It will be understood that theelectric motor may be suitably controlled by conventional means (notshown) so that the platform and the mechanism which it carries, may bemoved at any desired speed. The motion of the platform will obviously bealong the length of the slate or blackboard that is to be resurfaced.

The grinding element, which will be described more fully hereinafter, ispivotally supported above the platform by stanchions 29. The stanchions20 also support a vertically positioned tube 22 which extends upwardlyto a stub shaft 24 pivotally supported at the uppermost portion of thestanchion. The shaft 24 carries on its end United States Patent? G A2,828,587 Patented Apr. 1, 19 58 remote from the tube 22 a dual V-beltpulley 26. The larger of the dual pulley carries a V-belt 28 whichtravels around a pulley mounted on the shaft of a conventional electricmotor 30, which also is carried by the wheeled platform to. The end ofthe stub shaft 24 remote from the dual pulley 26 extends within a hollowtube or shaft 32 which is rotatably supported by the stub shaft 24 andthe tube 22. A disc 34 encircles the stub shaft 24 and the hollow shaft32, and is irrotationally secured to the stanchion 20.

An arm 36 is pivotally supported by the stub shaft 24 and extendsoutwardly to support a grinding element, generally identified as theelement 38. The grinding element 38 is preferably composed of a steelpan 40 having a peripheral lip 41, a sponge rubber disc.42, a relativelyhard rubber disc 44 and a sandpaper disc 46. These discs are suitablysecured, by the use of a conventional keyhole attaching means 47 to adisc 48 mounted on the hollow shaft 50.

The hollow shaft 50 extends through, and is secured to the end of thearm 36 remote from its pivotal connection on the stub shaft 24. Thehollow shaft 50 is directly connected with a tube 52 which extends alongthe arm 36 and is connected to the hollow tube orshaft 32, through whicha tube 54 extends to a suitable vacuum device 56. The grinding element38 is rotated by the rotation of the V-belt pulley 58, which in turn isrotated by the belt 69 passing over the smaller of the dual pulley 62.

The grinding element 38 is first positioned on the slate or blackboardto be reconditioned by the operator placing the grinding element 33 inproper position to grind the portion of the slate that is first to beground. This is done by his holding the handle 62 while positioning thegrinding head 38, and at the same time pushing the holding clamp 64inwardly (to the right as viewed in Figure 2) against the pressure ofthe spring 66, and thus releasing the friction stop 6% from its contacton the disc- 34. At the time that the grinding head has been placed inthe proper position to grind the slate that is to be reconditioned,pressure on the holding clamp 64 will be released and the grinding head38 will be maintained in its adjusted position.

The disc 48 is preferably secured to a hollow casing 70, from which aplurality of tubes 72 extend, and is affixed to the hollow casing 74aligned concentrically with the V-belt pulley 58. Thus, suction from thevacuum device 56 will draw air through the hollow shaft 50 directly fromthe sanding or grinding element 38 as it grinds from the slate orblackboard being resurfaced. Universal joints 78 are provided betweenthe hollow casings 70 and 74 to drive the grinding element 38, and toprovide flexibility so that the element can properly follow a sometimescurved surface of the slate being resurfaced.

It will readily be understood that an idler pulley 80 will be positionedto tension the belt 60 by the adjustment of the arm 82 pivoted to thearm 36.

The suction of the vacuum 56 will draw air around the grinding head 38from the periphery thereof, and will draw the same toward the slate orblackboard to be resurfaced. The suction being constant will maintainthe grinding head against the slate with unvarying pressure. The samesuction will not only draw and maintain the grinding head against theslate, but will also remove any particles that are ground from theboard. Also the suction will maintain a relatively cool sanding surface,thus preventing any melting or burning of the sanding paper.

After the grinding head has been positioned as described above, theplatform 10 will be moved lengthwise of the blackboard by the operationof the electric motor within the casing 12. The speed of movement may beable carriage, a stanchion upstanding on said carriage,

a grinding head supporting arm pivotally secured to said stanchion, ahollow stub shaft rotatably supported near the end of said supportingarm remote from said stan- "chion, a pulley secured to said hollow stubshaft, belt means driving said pulley, a grinding head mountedconcentrically with saidpulley on the side thereof remote from saidsupporting arm, vacuum means connected to said hollow stub shaft at itsend remote from said grinding head, and spring pressed frictional meansattached to said supporting arm and adapted to maintain the same "at anyadjusted angle relative to the said carriage.

2. An abrasive resurfacing machine including a movable carriage, astanchion upstanding on said carriage, a grinding head supporting armpivotally secured to said stanchion, a hollow stub shaft rotatablysupported near the end of said supporting arm remote from saidstanchion, a. pulley secured on said hollow stub shaft, means drivingsaid pulley, a grinding head mounted concentrically with said pulley onthe side thereof remote from said supporting arm, vacuum means connectedto said 'hollow' stub shaft at its end remote from said grinding head,and spring pressed frictional means attached to said supporting arm andadapted to maintain the same at any adjusted angle relative to saidcarriage, the said vacuum constantly drawing the grinding head againstthe surface being ground and resurfaced.

3. An abrasive resurfacing machine including a movable carriage, astanchion upstanding on said carriage, a grinding head supporting armpivotally secured to said stanchion, a hollow stub shaft rotatablysupported near the end of said supporting arm remote from saidstanchion, a pulley secured to said hollow stub shaft, means drivingsaid pulley, a grinding head mounted concen- 1 trically with said pulleyon the side thereof remote from said supporting arm, vacuum meansconnected to said hollow stub shaft at its end remote from said grindinghead, and spring pressed frictional means attached to said supportingarm and adapted to maintain the same at any selected angle relative tosaid carriage, said vacuum con stantly drawing said grinding headagainst the surface to be resurfaced with equal pressure and constantcooling and particle removal.

4. An abrasive resurfacing machine including a movable carriage, astanchion upstanding on said carriage, a grinding head supporting armpivotally secured to said stanchion, spring pressed frictional meansattached to said supporting arm adapted to maintain said arm in adjustedposition relative to said carriage, a hollow stub shaft rotatablysupported near the end of said supporting arm remote from saidstanchion, a pulley secured to said hollow stub shaft, means drivingsaid pulley, a grinding head mounted concentrically with said pulley onthe side thereof remote from said supporting arm, said grinding head andpulley being connected together and providing a direct air circulationpassage between the radial centers thereof, and vacuum means connectedto said stub shaft at its end attached to the said supporting arm, saidvacuum communicating directly with the face of the grinding head remotefrom said pulley.

5. An abrasive resurfacing machine including a movable carriage, avertically extending stanchion on said carriage, a supporting armpivotally secured to said stanchion near its point of attachment to saidcarriage, a hollow stub shaft rotatably secured to said arm at its endremote from said carriage, a pulley secured to said hollow stub shaft,means driving said pulley, a grinding head having an open radial centeraxially aligned with said pulley, an air passageway between the openradial center of the grinding head and the hollow stub shaft, and vacuummeans communicating with the stub shaft at its end connected to the saidsupporting arm.

References Cited in the file of this patent UNITED STATES PATENTS2,298,228 Pond et al. Oct. 6, 1942 2,299,198 Williams Oct. 20, 19422,319,023 Walker May 11, 1943 2,484,906 Pond et al. Oct. 18, 1949

